[dspillett]

If there is a way of saving the result and posting it to the server (caveat: I have no idea if there currently is, there almost certainly isn't in a "95 of web users will have a compatible client" sort of way) then you could use this to remove some CPU load when accepting images that you want to watermark before presenting to other users. If it is your image being watermarked you are unlikely to circumvent the process.

[scaturr]

Yes. Absolutely. The library includes a blob() function for converting a watermarked image to a blob for use with FormData. The site has a demo that does just this for uploading to S3. Any browser supporting File API, FormData, and typed arrays should have no problems. IE 10 is the earliest IE that supports these APIs out of the box, but there are polyfills for IE9. The other modern browsers have supported these APIs for a while now.

[dspillett]

Interesting. I didn't realise those things had progressed so far into "generally stable and usable" territory client-side - an occupational hazard due to most of our clients being stuck on IE8 so I only play with less ancient "standards" when I find time for projects outside the day-job. I really need to try arrange some proper play time for myself soon!